As the percent of fabric softener active compound goes down in a liquid fabric softening composition, the viscosity of the liquid fabric softening composition also goes down. However, thickness is a desirable property in liquid fabric softening compositions. Thickness connotes quality and richness of the product. In many countries in the world, liquid fabric softening compositions (usually aqueous dispersions of fabric softener actives) are made with low concentrations (e.g. 0.5-12%) of the fabric softener active. Often, to achieve the desired viscosity of the aqueous dispersion, expensive polymers or additives (such as stearyl alcohol) must be added. There is a long unmet need in the market for a fabric softener active that, when dispersed in water at low concentrations, affords high viscosity dispersions without the need for a significant, if any, amount of polymer or thickening additive.
In WO 2007/092020 fabric softener active compositions are described wherein the amount of tri-ester quat (TEQ), as a percentage of the combined total (to 100%) of mono-ester quat (MEQ), di-ester quat (DEQ) and triester quat, is greater than 25%. However, a disadvantage is that the inventive compositions require that the free fatty acid be less than 1% in all cases. In order to achieve a free fatty acid value of less than 1%, long reaction times are required which utilize a significant amount of energy considering reactions to produce fabric softener actives are run between 160 and 210 degrees Celsius. When longer reaction times are employed, in order to achieve a certain high level of TEQ, less biorenewable, sustainable fatty acid (or methyl ester) is needed and more non-renewable, petroleum-based amine hub, e.g. triethanolamine (TEA), is required. WO2007/092020 also teaches that the iodine value (IV) of the feed used to provide the alkyl chains should be 20 or below—in general, the lower the IV of the feed, the worse the storage stability of liquid compositions made from fabric softener actives utilizing that feed, since the more saturated the fatty acids that hydrolyze (especially at elevated temperatures of the liquid fabric softener composition), the more they will crystallize and increase viscosity.
Thus, there is a need for a fabric softener active which will produce high viscosity when dispersed into water at low concentrations. There is also a need to produce the fabric softener active in the most energy efficient way possible and with maximum aqueous dispersion viscosity building potential.